The present invention relates to the structure of a transformer, and more specifically to a transformer for use on an alternative power supply, for the purpose of the transmission and amplification of electronic signals. The invention also concerns the effects of electrical insulations.
An alternative power supply as the power source of a computer and its peripheral equipments must conform to electrical safety requirements. There are many international institutions specifying safety inspection standards on electrical items, such as UL, CSA, IEC, etc, and VDE's standards are considered be the most rigorous. The transformer is one of the major items on the list of safety inspections. As far as the safety structure is concerned, a transformer may be divided into a primary winding coil, a secondary winding coil and an iron core, as shown in FIG. 1B. The primary winding is the portion which connects directly with the input power, and has a higher potential; the potential of the second winding is usually lower, and it is a part which people can easily touch. The iron core then comes as a long conductor.
VDE's safety requirement with respect to transformers is summarized as follows:
______________________________________ Absolute resistance to pressure Safe distance ______________________________________ Between the primary 3 750 VAC for 1 min. 6 mm min. winding and the second winding. Between the primary 2 500 VAC for 1 min. 4 mm min. winding and the iron core. Between the second 500 VAC for 1 min. -- winding and the iron core. ______________________________________
Up to the present, to meet these above-mentioned requirements, in a traditional transformer, as shown in FIG. 1A, it is a common practice to apply an insulating tube 300 on both the beginning end and the closing end of both the primary winding 100 and the second winding 200. In addition, a clearance of a length no less than 3 mm must be maintained on both sides inside the winding coil in relation to the winding tube. Also at least three layers of tape 400 have to be wound between the primary and the second windings. Such a conventional type of transformer, because of the failure to employ automatic sleeving of the insulating tube, 300 requires more time and labor to manufacture, and is impractical for the application of automatic winding.